All of these numbers are probably making these teams very nervous, but the A's are the one to watch. They are 10-6 in July on the strength of great pitching, but the collapse of their offense this month might be a sign that they've been playing over their heads.
They do not have a lineup with established stars and their best hitters have weak track records. July is a small sample size (16 games) and some of the players struggling in July (Coco Crisp, Jed Lowrie) played fine in June. The A's are have been surprising people for a while now and are certainly capable of leading the league in scoring runs in August (as they did in April), but this could also be the first sign that they might struggle to score runs for the rest of the year.
They can still make the playoffs if they pitch well and the Rangers struggle, but it could make it very difficult to go deep in the playoffs.